Application of Ferritic Heat-resistant Steel In Boiler Seamless Steel Pipe

Ferritic heat-resistant steel has excellent thermal conductivity, low expansion coefficient, good intergranular corrosion resistance, stress corrosion resistance and low production cost. It is the preferred steel for seamless steel tube of boiler. It is 20g, 15CrMo, 12Cr1MoV, Cr5Mo, Cr9Mo, T11, T12, T22, T91, T92, etc.


Boiler seamless pipe is mainly used for:
1. Water wall pipe
It is used to absorb the radiant heat in the furnace and heat the water into saturated steam, while protecting the fireplace. The steel used for water wall tube usually needs certain room temperature and high temperature strength, good high temperature durability and creep resistance, excellent corrosion resistance, especially excellent welding performance.
The reduction atmosphere in the lower part of the boiler furnace causes the water wall tube to become thinner, which is more serious when using high sulfur coal.  According to the temperature of water wall tube, the steel types are different.


2. High temperature superheater / reheater
High temperature superheater tube: the saturated steam is heated to superheated steam of a certain temperature, which is divided into several heating stages.  Reheater pipe: it is used to send the steam completed to the boiler and then to the steam turbine for work.
The seamless tubes of the final superheater and reheater of the boiler have the highest performance requirements in the boiler assembly, under the most complex and severe service conditions, and are 30-35 ° C higher than the rated steam temperature. The boiler tube used has the endurance strength and
The creep strength also needs to meet certain corrosion resistance: the outer wall of the pipe material is resistant to smoke corrosion, dust particle corrosion and oxidation resistance.


3. Pipe and title
The outlet header, main steam pipe and reheat steam pipe are located outside the furnace, which are less affected by flue gas corrosion, and have lower requirements for corrosion resistance of materials, and the temperature of the pipe wall is basically equal to the steam temperature.
At present, pipes and headers are made of ordinary medium alloy ferritic heat-resistant steel, which has low coefficient of thermal expansion and high thermal conductivity.


In conclusion, boiler ferritic heat-resistant steel can work for a long time under high temperature, high pressure and steam corrosion. In this environment, the performance of steel will decline rapidly, which will affect the operation of equipment, and ferritic heat-resistant steel will be very good. Meet this need. However, due to its high temperature strength, it cannot be used at higher temperatures. For this reason, people are developing new ferritic heat-resistant steel, such as ODS steel, but the cost is high and it seems that it is not suitable for wide application.